Suairyu said:
The black bars were the result of you viewing a 4:3 image on a 5:4 screen. It's no different than watching a correct aspect ratio film on a 16:9 TV - there are big black bars in those cases, too. Film buffs dislike changing the aspect ratio of a film to make it fill the space of a TV screen, so why is it so different for gamers in PAL regions?
According to what I gathered by personal experience and documentation on the matter, the addition of black borders in PAL versions is just an unpleasant result of
not converting properly the original 480i format to 576i, which is simply put comprised of more lines than NTSC.
PAL has these extra lines on the same 4:3 screen space, but as an outcome of lazy conversion in that regard, they weren't used at all, being merely replaced instead with black intrusive borders.
As a direct example, please compare a *native* gameplay on an appropriate system (not through emulation) of Yoshi's Island both on its PAL and NTSC-U counterparts. There's literally a black hole of differences.
The speed may have been reproduced in an almost comparable manner, which is in itself doubtful since later Nintendo titles (like Mario 64 or OoT) are sensibly slowed down in their european editions, but the black borders really stand out and hinder their fidelity.
Had it been a simple drawback of 5:4 to 4:3 conversions, NTSC SNES titles would feature horizontal bars in the same exact way, which by empirical evidence isn't quite the case.
EDIT: BTW, I think you got the proportions inverted. It's the other way around: the native SNES image is 5:4, while the output is conceived to be on 4:3 screens.
Nevertheless, the system was designed from the start to do this ratio change on ALL versions. It doesn't affect the problems we're dealing with.